The present invention relates generally to a mailpiece stacking device and method. More particularly, the invention relates to a method and apparatus for a mailpiece-stacking device that is intended for use with large volume mail handling machines in which mailpieces are discharged from an addressing printer.
Mailpiece stacking machines are well-known and have been used successfully in conjunction with various mailpiece processing machines, such as inserting machines, mailpiece printing machines, mail stamp cancellation machines, and envelope printing machines. The mailpiece is generally conveyed to a stacking device as the envelope leaves the mailpiece-processing machine. There are conventional stacking devices in which mailpieces are processed along a horizontal path after the mailpiece processing function is completed. There are also conventional stacking devices in which mailpieces are transported in a vertical orientation along a dual belt transport system on a horizontal surface.
Stacking devices in which mailpieces are processed along a horizontal path typically eject mailpieces from a mail-processing machine onto elongated conveying belts. The mail pieces are transported under a pressure wheel that assists in registering the mailpieces as they are transported toward a stacking wall. The mailpieces are lined against the stacking wall until the stack of mailpieces contacts the pressure wheel. The stack of mailpieces must then be removed from the stacking device to avoid overfilling or overflowing.
The removed stack of mailpieces is then manually placed in a mail tray that is sent to the postal service. The user can take advantage of lower postal rates that are provided to users who place mailpieces in trays according to predetermined criteria. The predetermined criteria include maintaining the mailpieces in the exact order in which they were processed in the mail processing machine. Generally, the predetermined criteria relates to a reduction in the postal service""s handling of the mail from the mailers. The United States Postal Service (xe2x80x9cUSPSxe2x80x9d) offers several levels of discounts to mailers who conform to the predetermined criteria. The level of discount typically is based on the number of criteria met by the mailer. To maximize such postage discounts, the USPS requires that high volume mailers presort the mailpieces, apply a ZIP+4 bar code to each mailpiece, and package their mail into trays with each tray tagged in accordance with the Domestic Mail Manual.
To obtain the postal rate discounts, the consecutive order of the mailpieces that have been presorted and processed by the mail-processing machine needs to be maintained. There are different stacking devices that have been designed for use with mail processing machines that have different speeds and volumes of output. As an example, the method and apparatus of conventional xe2x80x9con-edgexe2x80x9d stacking devices in which the lead edge of the mailpieces is urged against a fixed registration surface or a stacking wall is one way of maintaining the consecutive order of the mailpieces. The mailpieces are overlapped or shingled to maintain a consecutive order as the mailpieces are transported on the conveying belts to accumulate against the stacking wall.
A serious limitation to existing on-edge stacking devices, however, is maintaining a shingled relationship of the mailpieces as the mailpieces accumulate behind each other at the stacking wall while stacking mailpieces processed by a high-speed mail-processing device. The stacking devices have been designed to have conveying belts provide transport to the mailpieces. The conveying belts move at a slower linear speed than the speed at which the mail-processing machine is ejecting the mailpieces; therefore, oftentimes, a mail piece will be projected onto the stacking device conveying belts from the mail processing machine and overlap the previous mail piece to create a shingled relationship of the mail pieces. Due to the irregularity of the speed of the mail processing equipment, gaps between mailpieces are created. Mailpieces will get xe2x80x9cbunched upxe2x80x9d at the end of the conveyor instead of shingling and maintaining the consecutive order. Mailpieces are forced out of the consecutive order in which they were processed in the mail-processing machine, resulting in a lower postage discount than would otherwise be granted to the mailer.
There are other stacking devices that transport mailpieces vertically along a dual belt transport followed by various forms of stacking mechanisms normally used with high speed and high volume mail processing equipment. High volume mail processing machines typically process and eject between 5,000 and 36,000 pieces of mail per hour. The majority of these devices stack received mailpieces in a vertical orientation on a horizontal surface. Typically, in this type of system, a high speed, on-edge stacking device, mailpieces are transported vertically in a controlled manner with the conveying belts on both sides of the mailpiece, i.e., a dual belt transport system. The mailpieces typically stop against some type of vertical registration surface. Although the reliability of stacking mailpieces in consecutive order is maintained with this type of stacking device, the cost and the size of the high speed, high volume stackers having dual belt transports often cannot be justified. Also, when the mailpieces are transported vertically along a dual belt transport system, the ink that has been printed on mailpieces by printing devices may smear.
Thus, what is needed to overcome the above-mentioned drawbacks is a cost-efficient stacking device for use with high-speed mail processing machines that can reliably stack mailpieces in consecutive order without smearing the ink on the mailpieces.
The present invention provides an apparatus for stacking mailpieces received from a mail-processing machine in consecutive order. The apparatus comprises a frame, a plurality of conveying sections, the plurality of conveying sections comprising a receiving conveying section having an upstream portion and a downstream portion and a stacking conveying section having an upstream portion and a downstream portion, the receiving conveying section is positioned at a first height at a right angle to the mail processing machine at the upstream portion and in line with the stacking conveying section at the downstream portion, wherein the stacking conveying section is at a second height and the first height is greater than the second height. There is also a ramp that extends from the downstream portion of the stacking conveying section. A first continuous belt extends along the receiving conveying section in a first direction positioned centrally along a second direction of the conveying section and has a top surface that extends above the receiving conveying section and contacts the mailpieces received from the mail processing machine. A plurality of second continuous belts extends along the stacking conveying section in the first direction and is positioned substantially at equal intervals extending along the second direction of the stacking conveying section. The plurality of second continuous belts has a top surface that extends above the stacking conveying section and contacts the mailpieces received from the receiving conveying section. The apparatus for mailpiece stacking also has a means for driving the first continuous belt at a first speed on the receiving conveying section in the first direction and for driving the plurality of second continuous belts at a second speed on the stacking conveying section in the first direction with the second speed of the plurality of belts being less than the first speed of the first continuous belt on the receiving conveying section. Also, there is an assembly for positioning the mailpieces received from the mail processing machine in a first direction on the single continuous belt of the receiving conveying section in a second direction adjustably mounted to the frame at the upstream portion of the receiving conveying section, wherein the receiving conveying section is located between the assembly and the mail-processing machine. There also is a means for positioning and guiding mailpieces connected to the frame at the downstream portion of the receiving conveying section. The means for positioning the mailpieces are normal force rollers that contact the receiving conveying belt to align the mailpieces at the receiving conveying section and guide the mailpieces onto the stacking conveying belt.
An alternative embodiment is shown in which an apparatus for stacking mailpieces received from an output device in consecutive order comprises a frame, a receiving conveying section having an upstream portion and a downstream portion and a stacking conveying section having an upstream portion and a downstream portion. The receiving conveying section is positioned at a first height and adjacent to a mail processing machine at the upstream portion and orthogonal to the stacking conveying section at the downstream portion. The stacking conveying section is at a second height. The first height is greater than the second height. There is a ramp that extends from the downstream portion of the stacking conveying section. Also, a first continuous belt extends along the receiving conveying section in a first direction, is positioned centrally along a second direction of the conveying section, and has a top surface that extends above the receiving conveying section contacting the mailpieces. There is also a second continuous belt that extends along the stacking conveying section in the second direction and is positioned along the first direction of the stacking conveying section, the continuous belt having a top surface which extends above the stacking conveying section and which contacts the mailpieces received from the mail processing machine. There additionally are means for driving the continuous belt at a first speed on the receiving conveying section in the first direction and for driving the belt at a second speed on the stacking conveying section in the second direction. The second speed of the plurality of belts is slower than the first speed of the continuous belt on the receiving conveying section. There is also a hold down means at the downstream portion of the receiving conveying section for positioning and guiding the mailpieces. The hold down means comprises normal force rollers that contact the receiving conveying belt to align the mailpieces at the receiving conveying section and guide the mailpieces onto the stacking conveying belt.
Also disclosed is a method of stacking mailpieces received from a mail-processing device, wherein the mailpiece has a long leading edge, a long trailing edge, a short leading edge and a short trailing edge is also disclosed. To begin, a first mailpiece from the mail-processing device is received in a first direction with the short edge leading. The mailpiece is deflected onto the onto moving conveying belt with the long edge leading, the moving conveying belt is moving in a second direction, the second direction is at a right angle to the first direction. Then a second mailpiece is received onto the conveying belt from the mail processing device in the first direction with the short edge leading. The second mailpiece is deflected onto the moving conveying belt with the long edge leading while the conveying belt is moving in a second direction. The second direction is orthogonal to the first direction. The movement of the first mailpiece on the moving conveying belt is continued under an adjustable hold down assembly that positions and guides the mailpieces. The hold down assembly comprises a plurality of normal force rollers. The first mailpiece is moved from the receiving conveying belt traveling at a first speed and positioned at a first height to the stacking conveying belt positioned at a second speed and a second height, the first speed is faster than the second speed, the first height is higher than the second height. Then the second mailpiece is guided onto the long edge trailing of the first mailpiece. The movement of the mailpiece toward the vertically sloped stacking ramp is continued until the mailpiece interfaces with the sloped stacking ramp.